1. some browsers no longer accept javascript: directly from the location bar, they need you to call the script from a bookmarklet




2. your syntax smells of wishful thinking. What you try here would never work that way

This syntax:

javascript:(function() { var s = document.createElement(script); s.src=somejsurl.js;document.getElementsByTagName(head)[0].appendChild(s)})()

might be a better start

To get this to execute, you would need to create an html page with

<a href=javascript:(function() { var s = document.createElement('script'); s.src='somejsurl.js';document.getElementsByTagName('head')[0].appendChild(s)})()>Exec</a>

using single quotes inside the href code and load and drag the Exec to the bookmarks

While testing, Chrome and Firefox has a command line you can use

If you want to create the script and not load it, you would need to inline the script in the button you created:

javascript:(function() { var b = document.createElement(button); b.onclick=function() { alert('hello')}; b.innerTHML='Hello';})()